Polycarbonates are a versatile class of resins. It is desirable to improve the chemical resistance and processing properties of polycarbonates without detrimentally affecting the other properties of polycarbonate. It is also desirable to reduce the price of polycarbonates by blending them with other polymers without reducing the properties of the polycarbonate.
U.S. Pat. No. 4,172,859 issued Oct. 30, 1979 to Epstein discloses a polymer blend comprising 60 to 99 weight percent of a matrix selected from the group consisting of polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) or polycarbonate (PC) and from 1 to 40 weight percent of a dispersed phase having a particle size from 0.01 to 1 micron. The dispersed phase is described in very broad terms, but generally appears to relate to random polymers which contain one or more of the following monomers: ethylene, CO, anhydrides of ethylenically unsaturated dicarboxylic acids, epoxides and aromatic sulfonyl azides. The present invention is distinct over Epstein in that it relates to a blend of PET and PC and a styrenic acrylate which is grafted onto a di- or tri- block copolymer. The matrix of the composition of the present invention is a continuous phase of a blend of PET and PC and some of the styrene acrylic polymers. The discontinuous phase is dispersed as particles having a size from 0.05 to about 3 microns. The discontinuous phase is believed to be composed of particles of rubber containing inclusions of the styrene acrylate terpolymer.
Derwent WPI accession number 87-356703/51 which is an abstract of Japanese Patent 63023954 in the name of Mitsubishi Rayon K.K. discloses a blend of PC/polyester/and a polymer which is a graft of a vinyl monomer onto a polyorganosiloxane rubber. The present invention does not contemplate the use of such a grafted polyorganosiloxane.
Derwent WPI accession number 84-147555/24 which is an abstract of E.P. 110222 in the name of General Electric discloses a blend comprising:
(i) 10-90 percent of a polyester PA1 (ii) 0.1-20 percent of linear polyethylene; and PA1 (iii)5-70 percent of a polycarbonate; and PA1 (iv) 2-25 percent of an impact modifier. PA1 (i) 10-90 weight percent of PC; PA1 (ii) 5-80 weight percent of PET; PA1 (iii)3-20 weight percent of a styrene-(meth)acrylic acid polymer grafted onto a conjugated diene; PA1 (iv) 0.5-10 weight percent of polyethylene; and PA1 (v) 0.5-10 weight percent of butyl rubber. PA1 (i) 30-89.5 weight percent of PET; PA1 (ii) 5-61.5 weight percent PC; and PA1 (iii) 5-50 weight percent of a polymer of styrene and acrylonitrile grafted onto a polybutadiene polymer. PA1 a) from 40 to 90 weight percent of one or more homo- and co-polycarbonates selected from the group consisting of hydroquinone, resorcinol and polyphenols of the formula ##STR1## wherein R.sub.1 , R.sub.2, R.sub.3, and R.sub.4 are independently selected from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom, and a C.sub.1-4 alkyl radical; and X is a bond or divalent radical selected from the group consisting of C.sub.1-10 alkylene radicals; C.sub.2-8 alkenylene radicals, and C.sub.6-8 cycloalkylene radicals; PA1 b) from 5 to 45 weight percent of a polymer comprising: PA1 c) from 5 to 45 weight percent of a graft copolymer comprising a terpolymer comprising: PA1 which terpolymer is grafted to from 2 to 20 parts by weight of linear and radial di- or tri- block copolymers having a molecular weight of not less than 75,000 and a styrene content from 20 to 50 weight percent selected from the group consisting of styrene-butadiene di-block copolymers, styrene-butadiene-styrene tri-block copolymers, styrene-isoprene di-block copolymers, styrene-isoprene-styrene tri-block copolymers, partially hydrogenated styrene-butadiene-styrene tri-block copolymers, and partially hydrogenated styrene-isoprene-styrene tri-block copolymers.
The present invention includes a styrene acrylate terpolymer which is not disclosed by this reference.
Derwent WPI accession number 87-076525/11 which is an abstract of Japanese 62030149 in the name of Teijin Chemicals K.K. discloses a blend comprising:
The present invention does not contemplate the use of butyl rubber.
Derwent WPI accession number 85-082543/14 which is an abstract of EP 135 904 in the name of Mobay discloses a polymer blend comprising:
The present invention does not contemplate the use of a graft polymer of the type disclosed in E.P. 135904.
U.S. Pat. No. 4,866,125 issued Sept. 12, 1989 assigned to Polysar Financial Services S.A. discloses blends of PC and a graft copolymer of the type used in the present invention. That patent does not disclose, nor suggest that such blends could be further blended with polyesters.
Accordingly the present invention seeks to provide a novel blend of polycarbonate, polyester and a stryene acrylate grafted onto a block copolymer. The polymer blends of the present invention have improved chemical resistance and processing properties. Optionally, the compositions of the present invention may further contain from 0 up to about 30 weight percent of a rubbery impact modifier.